Optical components used under conditions where the optical surface is exposed to particles may be impaired or damaged in their function by the impacting particles.
This problem can occur especially with mirrors for extreme UV radiation (XUV radiation) or soft X-rays. The XUV spectral range covers the wavelength range from about 10 nm to about 50 nm. To smaller wavelengths, the soft X-ray region follows, which comprises wavelengths from 1 nm to 10 nm. Here and in the following, soft X-ray radiation and XUV radiation shall be understood to mean the wavelength range from 1 nm to 50 nm. Mirrors for XUV radiation or soft X-rays can be used, for example, in semiconductor manufacturing, materials analysis or astronomy.
Laser-induced plasmas, especially based on tin, are frequently used as radiation sources for the generation of soft X-rays or XUV radiation. For beam shaping, a collector mirror is usually arranged in the vicinity of such a radiation source. However, the generation of radiation by laser-induced plasmas not only generates radiation, but also emits particles known as debris. In laser-induced plasmas, debris occurs among other things in the form of minute particles, for example, in the form of tin particles in tin-based plasmas. Debris can contaminate or damage optical components. Due to the spatial proximity of the collector mirror to the plasma, the collector mirror is particularly affected by damage and contamination by debris.